Yeast is not killed when milk is frozen. It is kind of like a cockroach...indestructable. I don't know where the reference is..maybe Kay Hoover's incredibly wonderful sheets on yeast, or in Lawrence, or Auerbach/Riordan. I know this to be true, however. That is why yeast is so pesky. kathleen Kathleen B. Bruce, BSN, IBCLC co-owner Lactnet,TLC, Indep. Consultant http://together.net/~kbruce/kbbhome.html LACTNET Archives http://library.ummed.edu/lsv/archives/lactnet.html LACTNET WWW http://www.telcomplus.com/~kga/lactation.html